1. Technical Field of the Invention
The present invention relates to liquid crystal devices which reduce wiring resistance, to manufacturing methods therefor, and to electronic apparatuses using the liquid crystal devices for display portions.
2. Description of the Related Art
As has been well known, since liquid crystal display devices have advantages in weight and electric power consumption compared to display devices using CRTs (cathode ray tubes), in particular, they are widely used for display portions of electronic apparatuses which are required to have portability.
Liquid crystal display devices generally have a structure in which two substrates are bonded to each other with a predetermined gap therebetween so that electrode forming surfaces thereof oppose each other, and liquid crystal is received in the gap; and when roughly classified in accordance with a driving mode, they can be classified into an active matrix type in which liquid crystal is driven by switching elements, and a passive matrix type in which liquid crystal is driven without using switching elements. In addition, the former, the active matrix type, can be further classified into a type which uses three-terminal elements, such as a thin-film transistor (TFT), as switching elements, and a type which uses two-terminal elements such as a thin-film diode (TFD).
The type which uses TFD elements as the switching elements among active matrix types and the simple passive matrix type have a structure in which scanning lines (common electrodes) are formed on one substrate and data lines (segment electrodes) are formed on the other substrate. Accordingly, in these types described above, since scanning signals (common signals) and data signals (segment signals) must be supplied by bonding an FPC substrate to each of the two substrates, problems of complicated bonding step and an increase in cost may arise. Accordingly, in the types described above, a technique has been proposed to bond one piece of FPC substrate to only one of the two substrates by using a structure in which all wirings or electrodes formed on the other substrate are connected to wirings formed on said one of the two substrates via conducting materials, that is, a structure is formed so that all wirings or electrodes formed on the other substrate are gathered on said one of the two substrates.
However, in the technique described above, the wirings formed on said one of the two substrates are composed of the same material as that used for transparent electrodes on said one of the two substrates, which apply a voltage to the liquid crystal. In this connection, as a material used for the transparent electrode mentioned above, ITO (Indium Tin Oxide) is generally used; however, the square resistivity of this transparent electrode material is high compared to that of a common metal. Accordingly, when the transparent electrode material described above is used for wirings for electrical connection in an area other than the display area, the resistance is naturally increased, and as a result, a problem may arise in that the image quality is adversely influenced.
In particular, recently, in order to reduce the number of connection points between a liquid crystal panel and a FPC substrate, driver ICs for driving the scanning lines (common electrodes) and the data lines (segment electrodes) are mounted on a glass substrate of the liquid crystal panel in some cases. In the case described above, various control signals and clock signals must be supplied to the driver ICs; however, when the transparent electrode material described above is used for wiring from the FPC substrate to the driver ICs, since the time constant is increased concomitant with an increase in wiring resistance, deformation of waveforms, a decrease in amplitude, and the like occur, and as a result, a problem may arise in that the operation margin is narrowed.
The present invention was made in view of the problems described above, and an object of the present invention is to provide a liquid crystal device which reduces resistance of wirings formed on a substrate, a manufacturing method therefor, and an electronic apparatus using the liquid crystal device for the display portion.
Accordingly, a liquid crystal device of one aspect of the present invention is a liquid crystal device having a first substrate and a second substrate, which are disposed to oppose each other, and liquid crystal enclosed in a gap between the first substrate and the second substrate, which comprises: a first transparent electrode provided on the first substrate; a first wiring provided on the second substrate; and a conductive material connecting the first transparent electrode and the first wiring; wherein the first wiring comprises a metal oxide film and a conductive film having a resistance lower than that of the metal oxide film. According to the structure described above, since the first wiring is a laminated film composed of a chemically stable metal oxide film and a chemically unstable conductive film having a resistance lower than that of the metal oxide film, compared a single layer composed of one of the two films described above, a lower resistance and improved stabilization of the wiring can be obtained.
In the structure described above, the conductive material is composed of nonconductive particles formed of, for example, a plastic covered with a metal such as gold (Au), and a metal oxide film generally has better adhesion with this covering metal. As a result, in the structure described above, the conductive film of the first wiring is preferably formed on an area other than the portion connecting with the conductive material.
In addition, preferably, the structure described above further comprises a driver IC provided on the second substrate for driving the liquid crystal, wherein the driver IC comprises an output side bump for supplying a signal, the output side bump is connected to the first wiring, and the conductive film is formed on an area other than the portion connecting with the driver IC. When the driver IC for driving the liquid crystal is mounted on the second substrate via the first wiring, the conductive material, and the first transparent electrode as described above, the number of connection points with the external can also be decreased. Furthermore, when the driver IC is bonded to the wiring, an adhesive having conductive particles dispersed therein is used, and similar to the conductive material described above, the conductive particles are formed of nonconductive particles such as a plastic covered with a metal such as gold (Au). Accordingly, when the conductive film is formed on an area other than the portion connecting with the driver IC, the metal oxide film and the covering metal contained in the conductive material are brought into contact with each other, and as a result, the adhesion therebetween is improved.
Furthermore, preferably, the structure described above further comprises a second wiring which is provided on the second substrate and which comprises a metal oxide film and a conductive film having a resistance lower than that of the metal oxide film; and a driver IC provided on the second substrate for driving the liquid crystal; wherein the driver IC comprises an input side bump for inputting a signal, the input side bump is connected to the second wiring, and the conductive film included in the second wiring is formed on an area other than the portion connecting with the driver IC. As a result, since the second wiring is a laminated film formed of a chemically stable metal oxide film and a chemically unstable conductive film having a resistance lower than that of the metal oxide film, compared to a single layer composed of one of the two films described above, a lower resistance of the wiring can be obtained. Accordingly, since the signals are supplied to the driver IC driving the liquid crystal via the second wiring having a lower resistance, the influence caused by voltage drop and the like can be suppressed to be small. In addition, when the metal oxide film is provided at the portion connecting with the driver IC without using the low-resistance conductive film, the adhesion with the covering metal contained in the conductive material can also be improved.
The liquid crystal device having the second wiring and the IC driver preferably further comprises a first protruding area which is provided in the vicinity of one edge of the second substrate and which does not overlap with the first substrate; and a second protruding area which is provided in the vicinity of another edge, intersecting said one edge, of the second substrate and which does not overlap with the first substrate; wherein the driver IC is provided on the first protruding area, and the second wiring is provided on the first protruding area and on the second protruding area.
In addition, structure described above preferably further comprises an external circuit substrate connected to the second wiring on the second protruding area; wherein the conductive film included in the second wiring is formed on an area other than the portion connecting with the external circuit substrate. Accordingly, signals can be supplied to the IC driver from the external circuit substrate via the second wiring having a lower resistance.
In addition, in the structure described above, it is also preferable that the liquid crystal device further comprise a second transparent electrode provided on the second substrate and a driver IC connected to the second transparent electrode. Accordingly, a signal can be supplied to the second transparent electrode by the driver IC.
In addition, the liquid crystal having the second transparent electrode and the IC driver, which are provided on the second substrate, preferably further comprises a second wiring which is provided on the second substrate and which comprises a metal oxide film and a conductive film having a resistance lower than that of the metal oxide film; a first protruding area which is provided in the vicinity of one edge of the second substrate and which does not overlap with the first substrate; and a second protruding area which is provided in the vicinity of another edge, intersecting said one edge, of the second substrate; wherein the driver IC is provided on the first protruding area and comprises an input side bump for inputting a signal from the second wiring, and the second wiring is provided on the first protruding area and on the second protruding area. In the structure described above, since the second wiring is a laminated film formed of a chemically stable metal oxide film and a chemically unstable conductive film having a resistance lower than that of the metal oxide film, compared to a single layer composed of one of the two films, a lower resistance and improved stabilization of the wiring can be obtained. As a result, since signals are supplied to the driver IC via the second wiring having a lower resistance, the influence of voltage drop and the like can be suppressed to be small.
In addition, in the structure described above, the conductive film included in the second wiring is preferably formed on an area other than the portion connecting with the driver IC. At the portion connecting with the driver IC, when the metal oxide film is provided without using the low-resistance conductive film, the adhesion of the metal oxide film with the covering metal contained in the conductive material can also be improved.
Accordingly, since an electronic apparatus according to another aspect of the present invention comprises the liquid crystal device described above, the wiring resistance is decreased, and as a result, adverse influence to the display quality and reduction in operation margin of the driving circuit can be prevented.
In addition, a liquid crystal device in accordance with another aspect of the present invention is a liquid crystal device having a first substrate and a second substrate, which are disposed to oppose each other, and liquid crystal enclosed in a gap between the first substrate and the second substrate, which comprises: a first transparent electrode provided on the first substrate; a first wiring provided on the second substrate; a conductive material connecting the first transparent electrode and the first wiring; a second transparent electrode provided on the second substrate; and a second wiring which is provided on the second substrate and which is connected to the second transparent electrode; wherein at least one of the first and the second wirings comprises a metal oxide film and a conductive film having a resistance lower than that of the metal oxide film. According to the structure described above, since the first and the second wirings are gathered on the second substrate, the connection with the external can be easily performed. In addition, since at least one of the first and the second wirings is a laminated film formed of a chemically stable metal oxide film and a chemically unstable conductive film having a resistance lower than that of the metal oxide film, compared to a single layer composed of one of the two films, a lower resistance and improved stabilization of the wiring can be obtained.
In the structure described above, the liquid crystal device preferably further comprises a driver IC provided on the second substrate for driving the liquid crystal; wherein the driver IC comprises an output side bump for supplying a signal, and the output side bump is connected to the first or the second wiring. As described above, when the driver IC connected to the first or the second wiring is mounted on the second substrate, the number of connection points with the external can be reduced.
In addition, in the structure described above, the liquid crystal device preferably further comprises an external circuit substrate supplying signals to each of the first and the second wirings. Accordingly, since signals are supplied from the external circuit substrate to the first and the second wirings, it is not necessary to mount an IC driver on the second substrate.
In addition, a liquid crystal device in accordance with another aspect of the present invention is a liquid crystal device having a first substrate and a second substrate, which are disposed to oppose each other, and liquid crystal enclosed in a gap between the first substrate and the second substrate, which comprises: a first protruding area which is provided in the vicinity of one edge of the second substrate and which does not overlap with the first substrate; a second protruding area which is provided in the vicinity of another edge, intersecting said one edge, of the second substrate and which does not overlap with the first substrate; and a wiring which is provided on the first protruding area and on the second protruding area; wherein the wiring comprises a metal oxide film and a conductive film having a resistance lower than that of the metal oxide film. According to the structure described above, since the wiring is a laminated film formed of a chemically stable metal oxide film and a conductive film having a resistance lower than that of the metal oxide film, even when the wiring is provided on the first and the second protruding portions, a lower resistance of the wiring can be obtained.
Furthermore, a liquid crystal device in accordance with another aspect of the present invention is a liquid crystal device having a first substrate and a second substrate, which are disposed to oppose each other, and liquid crystal enclosed in a gap between the first substrate and the second substrate, which comprises: a plurality of first transparent electrodes provided on the first substrate; a conductive shading film which is provided between the first transparent electrodes adjacent to each other and which is not in electrical contact with the first transparent electrodes; and wirings which are provided on the first substrate and which are connected to the transparent electrodes; wherein the wirings comprise substantially the same layer as that of the first transparent electrodes and substantially the same layer as that of the shading film. In the structure described above, since the layer used as the shading film on the first substrate is also used as the conductive layer having a lower resistance of the laminated wiring, without adding a specific step, a lower resistance of the wiring can be obtained.
In addition, a liquid crystal device in accordance with another aspect of the present invention is a liquid crystal device having a first substrate and a second substrate, which are disposed to oppose each other, and liquid crystal enclosed in a gap between the first substrate and the second substrate, which comprises: a plurality of first transparent electrodes provided on the first substrate; a conductive shading film which is provided between the first transparent electrodes adjacent to each other and which is not in electrical contact with the first transparent electrodes; a wiring provided on the first substrate; a second transparent electrode provided on the second substrate; and a conductive material connecting the wiring and the second transparent electrode; wherein the wiring comprises substantially the same layer as that of the first transparent electrodes and substantially the same layer as that of the shading film. In the structure described above, since the layer used as the shading film on the first substrate is also used as the conductive layer having a lower resistance of the laminated wiring, without adding a specific step, a lower resistance of the wiring can be obtained. In addition, the second transparent electrode provided on the second substrate is connected to the wiring provided on the first substrate by the conductive material. As a result, the connection with the external can be achieved only by connecting the first substrate therewith.
In addition, a method for manufacturing a liquid crystal device, in accordance with another aspect of the present invention, is a method for manufacturing a liquid crystal device having a first substrate and a second substrate, which are disposed to oppose each other, and liquid crystal enclosed in a gap between the first substrate and the second substrate, which comprises: a step of providing a first transparent electrode on the first substrate; a step of providing a first wiring on the second substrate; and a step of connecting the first transparent electrode and the first wiring by a conductive material; wherein the first wiring comprises a metal oxide film and a conductive film having a resistance lower than that of the metal oxide film. According to the method described above, since the first wiring is a laminated film formed of a chemically stable metal oxide film and a conductive film having a resistance lower than that thereof, compared to a single layer composed of one of the two films described above, a lower resistance of the wiring can be obtained.
Furthermore, a method for manufacturing a liquid crystal device, in accordance with another aspect of the present invention, is a method for manufacturing a liquid crystal device having a first substrate and a second substrate, which are disposed to oppose each other, and liquid crystal enclosed in a gap between the first substrate and the second substrate, which comprises: a step of providing a plurality of first transparent electrodes on the first substrate; a step of providing a conductive shading film between the first transparent electrodes adjacent to each other so as not to be in electrical contact with the first transparent electrodes; and a step of providing wirings connected to the first transparent electrodes on the first substrate; wherein the wirings are formed so as to comprise substantially the same layer as that of the first transparent electrodes and substantially the same layer as that of the shading layer. In the method described above, since the layer used as the shading film on the first substrate is also used as a conductive layer having a low resistance of the laminated wiring, without adding a specific step, a lower wiring resistance can be obtained.
In addition, a method for manufacturing a liquid crystal device, in accordance with another aspect of the present invention, is a method for manufacturing a liquid crystal device having a first substrate and a second substrate, which are disposed to oppose each other, and liquid crystal enclosed in a gap between the first substrate and the second substrate, which comprises: a step of providing a plurality of first transparent electrodes on the first substrate; a step of providing a conductive shading film between the first transparent electrodes adjacent to each other so as not to be in electrical contact with the first transparent electrodes; and a step of connecting a wiring provided on the first substrate and a second transparent electrode provided on the second substrate by a conductive material; wherein the wiring is formed so as to comprise substantially the same layer as that of the first transparent electrode and substantially the same layer as that of the shading layer. In the method described above, since the layer used as the shading film on the first substrate is also used as a conductive layer having a low resistance of the laminated wiring, without adding a specific step, a lower resistance of the wiring can be obtained, and in addition, the connection with the external can be achieved only by connecting the first substrate therewith.